Fixes 2 related issues:

1. wsconncache had incorrect logic to test whether to send DERPMap updates, sending if the maps were equivalent, instead of if they were not equivalent.
2. configmaps used a bugged check to test equality between DERPMaps, since it contains a map and the map entries are serialized in random order. Instead, we avoid comparing the protobufs and instead depend on the existing function that compares tailcfg.DERPMap. This also has the effect of reducing the number of times we convert to and from protobuf.